In an inverter for driving a compressor through a motor, preheating operation and liquid discharging operation are performed prior to the normal operation of the compressor. The preheating operation is an operation which preheats the motor for driving the compressor by causing a current to flow to the motor. The liquid discharging operation discharges the liquid refrigerant accumulated in the compressor into a refrigerant circulating path. In distinction from normal operation, the preheating operation and liquid discharging operation are regarded as preparatory operation.
When a boot capacitor is provided to function as an operating power supply for a high-arm-side transistor of the inverter, it is necessary to charge the boot capacitor. This charging operation may also be performed as preparatory operation. Alternatively, the boot capacitor may be charged while halting the operation after performing the preparatory operation, and then sift to normal operation is conducted. Or, the boot capacitor may be charged during normal operation.
Techniques related to the present invention include Patent Documents 1 to 4.
Patent Document 1: Japanese Patent Application Laid-Open No. 2005-337234
Patent Document 2: Japanese Patent Application Laid-Open No. 61-31859 (1986)
Patent Document 3: Japanese Patent Application Laid-Open No. 10-318173 (1998)
Patent Document 4: Japanese Patent Application Laid-Open No. 2001-186793